Metal ion mediated transfer and cleavage of diaminocarbene ligands

Article abstract of DOI:10.1021/om981023d

Under mild conditions, reactions of (CO)₅M=C[N(R)CH₂]₂ [M = W, Mo, Cr; R = Et, allyl, benzyl, 4-pentenyl] with (PhCN)₂PdCl₂, (PhCN)₂PtCl₂, [(CO)₂RhCl]₂, (Me₂S)AuCl, [(CH₃-CN)₄Cu]BF₄, and AgBF₄ provide the corresponding diaminocarbene complexes via carbene ligand transfer. The resulting Pd(II), Pt(II), Rh(I), and Au(I) carbene complexes are stable and were isolated. The Cu(I) and Ag(I) complexes readily undergo acid-induced M=C cleavage to yield the imidazolidin-2-ylidinium salts. The carbene-transfer reactions were studied for two phosphine donors: (CO)_m(L)W=C[N(R)CH₂]₂ {R = Et, benzyl; L = PPh₃, m = 4; L = dppe, m = 3}. The X-ray crystal structures of (CO)₅W=C[N(CH₂C₆H₅)CH ₂]₂ (1c), cis-(CO)₄-(PPh₃)W=C[N(CH₂C₆H ₅)CH₂]₂ (5b), fac-(CO)₃(dppe)W=C[N(CH₂C₆H₅)CH ₂]₂ (6b), Cl₂(CO)-Pt=C[N(CH₂C₆H₅)CH ₂]₂ (9c), and cis-Cl₂Pt{=C[N(CH₂C₆H₅)CH ₂]₂}₂ (11b) are reported.

Full text of DOI:10.1021/om981023d

Organometallics 1999, 18, 2145-2154
2145
Meta l Ion Med ia ted Tr a n sfer a n d Clea va ge of
Dia m in oca r ben e Liga n d s
Rong-Zhi Ku,† J en-Chung Huang,† J ian-Yang Cho,† Fu-Mei Kiang,‡
K. Rajender Reddy,† Yi-Chun Chen,† Kuo-J eng Lee,† J ung-Hua Lee,†
Gene-Hsiang Lee,† Shie-Ming Peng,† and Shiuh-Tzung Liu*,†
Department of Chemistry, National Taiwan University, Taipei, Taiwan 106 ROC, and
Department of Pharmacy, China Medical College, Taichung, Taiwan ROC
Received December 16, 1998
Under mild conditions, reactions of (CO)5MdC[N(R)CH2]2 [M ) W, Mo, Cr; R ) Et, allyl,
benzyl, 4-pentenyl] with (PhCN)2PdCl2, (PhCN)2PtCl2, [(CO)2RhCl]2, (Me2S)AuCl, [(CH3-
CN)4Cu]BF4, and AgBF4 provide the corresponding diaminocarbene complexes via carbene
ligand transfer. The resulting Pd(II), Pt(II), Rh(I), and Au(I) carbene complexes are stable
and were isolated. The Cu(I) and Ag(I) complexes readily undergo acid-induced MdC cleavage
to yield the imidazolidin-2-ylidinium salts. The carbene-transfer reactions were studied for
two phosphine donors: (CO)m(L)WdC[N(R)CH2]2 {R ) Et, benzyl; L ) PPh3, m ) 4; L )
dppe, m ) 3}. The X-ray crystal structures of (CO)5WdC[N(CH2C6H5)CH2]2 (1c), cis-(CO)4-
(PPh3)WdC[N(CH2C6H5)CH2]2 (5b), fac-(CO)3(dppe)WdC[N(CH2C6H5)CH2]2 (6b), Cl2(CO)-
PtdC[N(CH2C6H5)CH2]2 (9c), and cis-Cl2Pt{)C[N(CH2C6H5)CH2]2}2 (11b) are reported.
In tr od u ction
under mild conditions, indicating that a carbene-
transfer reaction between transition metal complexes
can be facile.12 To gain insight into such carbene
transfer, an investigation of the reactvities of diamino-
carbene complexes 1-4 toward other transition metal
ions was conducted. Herein we report the carbene
Fundamental studies of synthetic approaches and
properties of transition metal carbene complexes are
still an interesting area of research.1,2 Several synthetic
approaches have been established for the preparation
of metal carbene complexes,3-11 but few investigations
involving carbene transfer between metal ions to gener-
ate new carbene species have been reported.4
Diamino-substituted carbenes are unusually stable
due to the good σ-donating ligand.5-11 It occurred to us
that the stable diaminocarbene makes them suitable for
studying carbene transfer between metal ions. In a
preliminary report, we showed that carbene complexes
of Pd(II), Pt(II), Rh(I), and Au(I) were formed in high
yields via the reaction of tungsten diaminocarbene
complexes [(CO)5WdCNRCH2CH2NR] with (PhCN)2-
PdCl2, (PhCN)2PtCl2, [(CO)2RhCl]2, and (Me2S)AuCl
(5) (a) Arduengo, A. J ., III; Harlow, R. L.; Kline, M. J . Am. Chem.
Soc. 1991, 113, 361. (b) Arduengo, A. J ., III; Dias, H. V. R.; Calabrese,
J . C.; Davidson, F. Organometallics 1993, 12, 3405. (c) Arduengo, A.
J ., III; Dias, H. V. R.; Calabrese, J . C.; Davidson, F. Inorg. Chem. 1993,
32, 1541. (d) Arduengo, A. J ., III; Tamm, M.; McLain, S. J .; Calabrese,
J . C.; Davidson, F.; Marshall, W. J . J . Am. Chem. Soc. 1994, 116, 7927.
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J . Am. Chem. Soc. 1994, 116, 4391. (f) Arduengo, A. J ., III; Krafczyk,
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1997, 365. (h) Arduengo, A. J ., III; Harlow, R. L.; Marshall, W. J .;
Prakasha, T. K. Heteroat. Chem. 1996, 7, 421. (i) Arduengo, A. J ., III;
Calabrese, J . C.; Cowley, A. H.; Dias, H. V. R.; Goerlich, J . R.; Marshall,
W. J .; Riegel, B. Inorg. Chem. 1997, 36, 2151. (j) Arduengo, A. J ., III;
Dias, H. V. R.; Calabrese, J . C. Chem. Lett. 1997, 143. (k) Arduengo,
A. J ., III; Carmalt, C. J .; Clyburne, J . A. C.; Cowley, A. H.; Pyati, R. J .
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Goerlich, J . R.; Krafezyk, R.; Marshall, W. J . Angew. Chem., Int. Ed.
Engl. 1998, 37, 1963, and references therein.
(6) (a) Herrmann, W. A.; Elison, M.; Fischer, J .; Ko¨cher, C.; Artus,
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Goossen, L. J .; Spiegler, M. Organometallics 1998, 17, 2162. (d)
Herrmann, W. A.; Goossen, L. J .; Spiegler, M. J . Organomet. Chem.
1997, 547, 357. (e) Herrmann, W. A.; Elison, M.; Fischer, J .; Ko¨cher,
C.; Artus, G. R. J . Angew. Chem., Int. Ed. Engl. 1995, 34, 2371 (f)
Herrmann, W. A.; Munck, F. C.; Artus, G. R. J .; Runte, O.; Anwander,
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Artus, G. J . Organomet. Chem. 1995, 501, C1. (h) Herrmann, W. A.;
Koecher, C.; Goossen, L. J .; Artus, G. R. J . Chem. Eur. J . 1996, 2, 1627.
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Organometallics 1995, 14, 1085. (j) Herrmann, W. A.; Goossen, L. J .;
Artus, G. R. J .; Ko¨cher, C. Organometallics 1997, 16, 2472. (k)
Herrmann, W. A.; Goossen, L. J .; Ko¨cher, C.; Artus, G. R. J . Angew.
Chem., Int. Ed. Engl. 1996, 35, 2805. (l) Ko¨cher, C.; Herrmann, W. A.
J . Organomet. Chem. 1997, 532, 261. (m) Herrmann, W. A.; Fischer,
J .; O¨ fele, K.; Artus, G. R. J . J . Organomet. Chem. 1997, 530, 259, and
references therein.
* E-mail: stliu@ccms.ntu.edu.tw.
† National Taiwan University.
‡ China Medical College.
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10.1021/om981023d CCC: $18.00 © 1999 American Chemical Society
Publication on Web 05/06/1999

2146 Organometallics, Vol. 18, No. 11, 1999
Ku et al.
Ta ble 1. Som e Sp ectr a l Da ta of Gr ou p VI Meta l
Ca r bon yl Dia m in oca r ben esa
transfer from group VI metal carbonyl complexes to
other transition metal ions and the cleavage of the
M-C(carbene) bond by copper and silver ions.
b
complex
δ of carbene carbon
νCO (cm-1
)
ref
1a
1b
1c
1d
2a
2b
3a
3b
3c
4
205.6 (J W-C ) 95.7 Hz) 2062, 1919
208.0 (J W-C ) 95.8 Hz) 2063, 1920
209.1 (J W-C ) 95.1 Hz) 2064, 1922
207.2 (J W-C ) 96.0 Hz) 2062, 1919
11
11
this work
this work
11
11
11
11
214.1
215.9
219.2
220.6
221.6
2063, 1928
2064, 1928
2054, 1929
2064, 1928
2056, 1924
this work
216.8 (J W-C ) 91.7 Hz) 2022, 1918, 1863 11
5a
5b
6a
6b
214.1 (J P-C ) 8.4 Hz)
217.6 (J P-C ) 8.3 Hz)c
210.8 (J P-C ) 5.9 Hz)
210.2 (J P-C ) 6 Hz)c
2002, 1874, 1853 this work
2004, 1876, 1854 this work
1919, 1820
1921, 1824
this work
this work
a
b
13C NMR in CDCl3. IR in CH2Cl2. c In CD3COCD3.
Resu lts a n d Discu ssion
P r ep a r a tion of Ca r ben e Com p lexes. All carbene
complexes were prepared by the method previously
reported for the N-benzyl-substituted complexes (1c, 2c,
and 3c). The π-coordinated diaminocarbene complex 4
is obtained thermally by heating 1b above 100 °C.
Substitution reactions of 1a and 1c with triphenylphos-
phine or bis(diphenylphosphino)ethane (dppe) proceeded
cleanly at 120 °C to produce 5a ,b and 6a ,b, respectively,
in excellent yields.
All the carbene complexes were isolated as stable
solids and characterized by both spectral and elemental
analyses. Some spectral data are summarized in Table
1. The facial geometry of complexes 6 and the cis
arrangement in 5 were established by 31P NMR chemi-
cal shifts and their IR carbonyl stretching patterns.
X-ray single-crystal structures of 5b and 6b were
obtained to provide confirmation (see Crystallography
section).
(PhCN)2PdCl2, (PhCN)2PtCl2, [(CO)2RhCl]2, and (Me2S)-
AuCl results in the formation Pd(II), Pt(II), Rh(I), and
Au(I) carbene complexes, respectively, in high yields.
Further investigation showed that the chromium and
molybdenum diaminocarbene complexes with different
N-substituents (2, 3) behave similarly. Structural varia-
tions in the carbene transfers are summarized in
Scheme 1.
P a lla d iu m -Ca r ben e Com p lexes. The N-substitu-
ent in complexes 1a -1d affects the carbene transfer
dramatically with respect to both reaction rate and
structure. Complex 1a reacts with an equimolar amount
of (PhCN)2PdCl2 to yield the chloro-bridged dipalladium
carbene complex 7a , whereas complexes 1b-d give
biscarbene palladium species upon treatment with
(C6H5CN)2PdCl2. Reactions of 1b-d leading to 7b-d
were complete within 0.5 h at ambient temperature,
while reaction of 1a required 2 h under refluxing
conditions. These observations indicate that the π-bond
functionality on the nitrogen atom accelerates the
carbene transfer and influence the structure of the
products.
Transformation of the carbene ligand from other
group VI metal ions to palladium proceeds similarly.
Thus, complexes 2a ,b and 3a ,b react with (PhCN)2PdCl2
to yield carbene complexes 7a ,b as the exclusive prod-
uct. The ligands around the palladium metal center
influence the carbene-transfer reaction; for example,
none of the complexes (CH3CN)2PdCl2, (Ph3P)2PdCl2,
(COD)PdCl2, or (COD)Pd(Me)Cl [COD ) 1,5-cycloocta-
diene] reacts with tungsten complexes to generate
palladium carbenes. This result shows that a weak
coordinating ligand is essential for the carbene transfer.
Significantly, the π-coordinating carbene 4 does not
react with (PhCN)2PdCl2, indicating that the carbene
transfer is affected by the ligand surrounding the group
VI metal center.
Ca r ben e-Tr a n sfer Rea ction s. The diaminocarbene
unit of group VI metal carbonyl complexes 1-3 is
readily transferred to the other transition metal ions.
We reported earlier that reaction of 1a and 1b with
(8) (a) Enders, D.; Breuer, K.; Runsink, J .; Teles, J . H. Liebigs Ann.
1996, 2019. (b) Enders, D.; Gielen, H.; Raabe, G.; Runsink, J .; Teles,
J . H. Chem. Ber. 1996, 129, 1483. (c) Enders, D.; Gielen, H.; Breuer,
K. Tetrahedron Asymmetry 1997, 8, 3571. (d) Enders, D.; Gielen, H.;
Runsink, J .; Breuer, K.; Brode, S.; Boehn, K. Eur. J . Inorg. Chem. 1998,
913, and references therein.
(9) Regitz, M. Angew. Chem., Intl. Ed. Engl. 1996, 35, 725, and
references therein.
(10) (a) Kernbach, U.; Ramm, M.; Luger, P.; Fehlhammer, W. P.
Angew. Chem., Intl. Ed. Engl. 1996, 35, 310. (b) Kuhn, N.; Bohnen,
H.; Fahl, J .; Bla¨ser, D.; Boese, R. Chem. Ber. 1996, 129, 1579. (c)
Schumann, H.; Glanz, M.; Winterfeld, J .; Hemling, H.; Kuhn, N.; Kratz,
T. Chem. Ber. 1994, 127, 2369. (d) Chamizo, J . A.; Hitchcock, P. B.;
J asim, H. A.; Lappert, M. F. J . Organomet. Chem. 1993, 451, 89. (e)
Maier, G.; Enders, J . Eur. J . Org. Chem. 1998, 1517. (f) Beck, G.;
Fehlhammer, W. P. Angew. Chem., Int. Ed. Engl. 1988, 27, 1344. (g)
Lappert, M. F.; Pye, P. L. J . Chem. Soc., Dalton Trans. 1977, 1283.
(h) Cardin, D. J .; Cetinkaya, B.; Lappert, M. F. Chem. Rev. 1972, 72,
545. (i) Lappert, M. F. J . Organomet. Chem. 1988, 358, 185. (j)
Sellmann, D.; Allmann, C.; Heinemann, F.; Knoch, F.; Sutter, J . J .
Organomet. Chem. 1997, 541, 291. (k) Aumann, R.; Fischer, E. O.
Chem. Ber. 1981, 114, 1853. (l) Guerret, O.; Sole´, S.; Gornitzka, H.;
Teichert, M.; Trinquier, G.; Bertrand, G. J . Am. Chem. Soc. 1997, 119,
6668. (m) Green, M. J .; Cavell, K. J .; Skelton, B. W.; White, A. H. J .
Organomet. Chem. 1998, 554, 175. (n) Wacker, A. Pritzkow, H.; Siebert,
W. Eur. J . Inorg. Chem. 1998, 843. (o) Zhang, S.-W.; Ishii, R.;
Takahashi, S. Organometallics 1997, 16, 20. (p) Araki, S.; Yamamoto,
K.; Yagi, M.; Inoue, T.; Fukagawa, H.; Hattori, H.; Yamamura, H.;
Kawai, M.; Butsugan, Y. Eur. J . Org. Chem. 1971, 36, 2607, and
references therein.
Typical 13C chemical shifts of carbene-carbon in the
palladium complexes are summarized in Table 2. The
13C resonances of the carbene center shift upfield from
(11) Liu, C.-Y.; Chen, D.-Y.; Cheng, M.-C.; Peng, S.-M.; Liu, S.-T.
Organometallics 1996, 15, 1055.
(12) Liu, S.-T.; Hsieh, T.-Y.; Lee, G.-H.; Peng, S.-M. Organometallics
1998, 17, 993.

Cleavage of Diaminocarbene Ligands
Organometallics, Vol. 18, No. 11, 1999 2147
Sch em e 1. Ca r ben e Tr a n sfer betw een Tr a n sition Meta l Ion s
Ta ble 2. 13C Ch em ica l Sh ifts of MdC(ca r ben e) in Va r iou s Com p lexesa ,b
N-substituent
M ) Pd
M ) Pt
M ) Rhb
M ) Au
R ) Et
173.3 (7a )
198.7 (7b)
199.1 (7c)
198.6 (7d )
174.3 (10a )
168.2 (10b)
212.8 (12a ) [36.9]
202.8 (12b) [30.3]
212.4 (12c) [37.7]
212.5 (12d ) [36.4]
203.8 (13a )
205.1 (13b)
204.4 (13c)
204.2 (13d )
R ) allyl
R ) benzyl
R ) 4-pentenyl
R ) Et
R ) benzyl
R ) 4-pentenyl
169.7(10d )
166.5 (9a )
168.2 (9a )
167.4 (9d )
a
b
Numbers given in parentheses are the labeling of complexes through the text. In CDCl3. c Number given in brackets are the values
of J Rh-C in Hz.
207-209 ppm for 1b-d to 198-199 ppm for 7b-d . This
upfield shift for palladium(II) complexes relative to the
group VI metal complexes was also observed in the
related imidazol-2-ylidene species.6d-f The structure of
7a was confirmed by X-ray diffraction.11 The trans-
biscarbene complex 7b slowly isomerizes to the more
stable cis-product 8, which was synthesized by Lappert
and co-workers via a different route.13
suggests a similar donating ability for diaminocarbene
and trialkylphosphine ligands, which has been previ-
ously discussed.5-8 The phosphine-substituted complex
11a ,b is obtained by treatment of 9a or 9c with
triphenylphosphine, and the olefin-substituted complex
10d is achieved intramolecularly via the thermal reac-
tion of 9d in refluxing chloroform. As with the palladium
complexes, platinum biscarbenes are obtained by the
treatment of the carbonyl-carbene complex 9a with
Me3NO to afford 10a . The N-allyl-substituted biscar-
bene complex 10b is obtained directly from the reaction
of 1b with (PhCN)2PtCl2 in refluxing chloroform, sug-
gesting that the formation of biscarbene metal com-
plexes is due to the strong σ-donating property of
diaminocarbenes. The chemical shift of the carbene
center in 10b (168.2 ppm) appears much upfield com-
pared to that of the palladium complex 7b.
13C NMR data for the platinum complexes are col-
lected in Table 2. NMR spectra of the platinum com-
plexes 11a ,b are similar to the palladium complexes.
Crystal structural determinations of 9c and 11b con-
firmed the proposed structure (see Crystallography
section).
Rh od iu m (I)- a n d Gold (I)-Ca r ben e Com p lexes.
Carbene ligand transfer reactions were also observed
with rhodium(I) and gold(I) metal ions. Substitution of
a carbonyl ligand by diaminocarbene at the rhodium(I)
center occurs in the reaction of 1a , 1c, and 1d with
P la tin u m -Ca r ben e Com p lexes. Unlike palladium,
both carbene and carbonyl ligands were transferred
from tungsten to platinum in several cases. Reactions
of 1a , 1c, and 1d with (PhCN)2PtCl2 in dichloromethane
yielded 9a , 9c, and 9d . The infrared carbonyl absorption
appears in the range 2100-2110 cm-1, which is es-
sentially identical to that in cis-(R3P)(CO)PtCl2.14 This
(13) (a) Cetinkaya, B.; Cetinkaya, E.; Lappert, M. F. J . Chem. Soc.,
Dalton Trans. 1973, 906. (b) Lappert, M. F.; Pye, P. L. J . Less-Common
Met. 1977, 54, 191.
(14) Mok, C. Y.; Tan, S. G.; Chan, G. C. Inorg. Chem. Acta 1990,
176, 43.

2148 Organometallics, Vol. 18, No. 11, 1999
Ku et al.
Ta ble 3. Som e Sp ectr oscop ic Da ta of Cop p er a n d
Silver Ca r ben e Com p lexesa
compd
δ of MdC (carbene)
MS FAB m/z (cation)
15a
197.0
315{C14H28N463Cu}
317{C14H28N465Cu}
363{C18H28N463Cu}
365{C18H28N465Cu}
363{C34H36N463Cu}
565{C34H36N465Cu}
359{C14H28N4107Ag}
361{C14H28N4109Ag}
15b
15c
16a
198.6
197.8
[Rh(CO)2Cl]2 to form biscarbene rhodium complexes
12a , 12c, and 12d , respectively. With a N-allyl sub-
stituent, the π-coordinated product 12b is obtained
directly under the same reaction conditions. The 13C
NMR chemical shift of the carbene C appears around
200-215 ppm with a rhodium-carbon coupling [average
J Rh-C ∼ 35 Hz].6b,10d,15
202.5
(J 107Ag-C ) 168 Hz,
J 109Ag-C ) 192 Hz)
204.2
(J 107Ag-C ) 169 Hz,
J 109Ag-C ) 194 Hz)
204.0
16b
16c
407{C18H28N4107Ag}
409{C18H28N4109Ag}
607{C34H36N4107Ag}
609{C34H36N4107Ag}
(J 107Ag-C ) 170 Hz,
J 109Ag-C ) 196 Hz)
The gold biscarbene complexes 13a -d are formed
directly via the reaction of 1a -d with (Me2S)AuCl
(Scheme 1) in dichloromethane at room temperature.
The gold biscarbene complexes are similar to those
prepared by the direct ligand substitution reaction of
LAuCl (L ) PPh3, Me2S) with C-imidazoyllithium.16
Carbene transfer from tungsten to gold(I) has been
reported by Fischer and Bock in the reaction of (CO)5Wd
C(R)NR′2 with HAuCl4 (eq 1).17 13C resonances for the
carbene-carbon of 13a -d (Table 2) are in the range
203-205 ppm, which is in agreement with related gold
complexes.16
a
In CDCl3.
(CH3CN)4]BF4 were trapped by adding a three equimo-
lar amount of 1,2-bis(diphenylphosphino)ethane (dppe)
to the reaction mixture. A copper complex of formula of
[Cu(dppe)2]BF4 was obtained in a quantitative yield
based on the amount of copper reagent used, indicating
that the copper ion retains its oxidation state. Tungsten
products W(CO)4(dppe), W(CO)3(dppe)(CH3CN), and
other substitution complexes were identified by spec-
troscopic means. Hexacarbonyltungsten was recovered
in up to 60% yield (based on the carbene complex used)
when the reaction was carried out in the presence of
an atmosphere of carbon monoxide.
Cop p er - a n d Silver -Ca r ben e Com p lexes. A NMR
tube containing a freshly dried CDCl3 solution of 1a and
0.5 mol equiv of [Cu(CH3CN)4]BF4 was studied by both
1H and 13C NMR. Clean spectra were observed, consist-
ing of peaks due to two species: the biscarbene copper
species 15a and a trace of N,N-diethylimidazolidinium
salt 14a (less 5% by integration). Selected 13C NMR
chemical shifts are summarized in Table 3. The chemi-
cal shifts and splitting patterns of copper and silver
biscarbene complexes are similar to that of the stable
bis(imidazol-2-ylidene) copper complex 18a , which was
isolated by Arduengo and co-workers.5b The range of
chemical shifts for the carbene moiety in 15a -c and
16a -c is downfield of that in 18a ,b, reflecting a
difference in π-delocalization in these N-heterocyclic
carbenes. Unlike 18a , the copper complexes in this work
are highly sensitive toward air and moisture and readily
decompose. In fact, the copper carbene complexes 15a -c
in dichloromethane readily convert into the correspond-
ing cyclic urea when exposed to air (eq 2). This may be
Ca r ben e Tr a n sfer a n d Clea va ge of MdC. Reac-
tion of [Cu(CH3CN)4]BF4 with an equimolar amount of
1a in refluxing acetonitrile results in the cleavage of
the carbene moiety to yield the imidazolidin-2-ylidinium
salt 14a quantitatively. A deuterated product at C2 is
obtained when acetonitrile-d3 or a mixture of tetrahy-
drofuran and D2O is used. This outcome suggests that
the additional hydrogen originated from the solvent.
Cleavage of metal carbene is also observed in the
reaction of 1a with Cu(II) or Ag(I) ions. Therefore, the
reaction of 1a with an equimolar amount of Cu(BF4)2‚
6H2O or AgBF4 in an acetonitrile solution provides 14a
as the exclusive product. Other N-substituted complexes
such as 1b,c, as well as group VI carbene complexes
2a ,b and 3a -c, undergo similar reactions to give
N-substituted imidazolidin-2-ylidinium salts 14a -c,
respectively. Treatment of 4 with an equimolar amount
of [(CH3CN)4Cu]BF4 in acetonitrle results in the cleav-
age of carbene ligand to yield 14b.
To understand the role of metal ions in these reac-
tions, metal complexes from the reaction of 1a with [Cu-
due to the less steric bulkiness of the N-alkyl substit-
uents and the nonaromaticity of the N-heterocyclic
carbene ring. Due to the contamination of trace tungsten
complexes and difficulty of purification, attempts to
obtain acceptable elemental analysis of these carbene
complexes failed, but these copper complexes were
(15) (a) Werner, H. J . Organomet. Chem. 1995, 500, 331. (b) Werner,
H.; Schwab, P.; Bleuel, E.; Mahr, N.; Steinert, P.; Wolf, J . Chem. Eur.
J . 1997, 3, 1375. (c) Schwab, P.; Werner, H. J . Chem. Soc., Dalton
Trans. 1994, 3415.
(16) Bonati, F.; Burini, A.; Pietroni, B. R. J . Organomet. Chem. 1989,
375, 147.
(17) Fischer, E. O.; Bock, M. Monatsh. Chem. 1984, 115, 1159.

Cleavage of Diaminocarbene Ligands
Organometallics, Vol. 18, No. 11, 1999 2149
Sch em e 2. P r op osed Rea ction P a th w a y for MdC
obtained (eq 3), indicating that the formation of urea
stems from the reaction of copper carbene with O2.
Clea va ge
Oth er Ca r ben e-Tr a n sfer Rea ction s. It was re-
ported recently by Lin and co-workers4g that imidazol-
2-ylidene silver complexes react with (CH3CN)2PdCl2 to
yield the corresponding palladium carbene. In our
studies, we found that treatment of palladium complex
7b or platinum complex 10b with AgBF4 readily causes
the cleavage of MdC to yield 14b. Presumably the
formation of 14b is similar to the reaction of 1-3 with
AgBF4, e.g., the formation of silver carbene complex 16b,
which then undergoes the cleavage reaction. No carbene
ligand transfer from silver to palladium ion was ob-
served. This result is attributed to the stronger basicity
of the simple diaminocarbenes (nonaromatic heterocyclic
carbene).6b,18
characterized spectroscopically. The mass spectrum
(FABMS) of 15a gave cations at m/z 315, 317 in the ratio
of 2:1, which accords with the ratio of natural abun-
dance of 63Cu and 65Cu. Similar observations also appear
with complexes 16b,c (Table 3). The observed coupling
from 107Ag and 109Ag nuclei to the carbene-C suggests
coordination of the carbene ligands to the metal center,
which is in accordance with observations by Arduengo
and co-workers concerning 18b.5b
Liga n d Effect. The reactivity of the diaminocarbene
moiety in the transfer reaction is sensitive to the ligands
around the tungsten center. It was found that 1a , 1c,
and 4 do not react with excess S8 in tetrahydrofuran
under refluxing conditions. This is a consequence of the
combination of the strongly donating character of di-
aminocarbene ligand and the strongly π-acid carbonyls
around the tungsten center. The phosphine-substituted
complexes 5a ,b and 6a ,b readily react with sulfur to
form the cyclic thiourea (eq 4). Apparently, the σ-donat-
ing phosphine ligands change the electronic environ-
ment of the metal center and allow the carbene ligand
to be oxidized, which is similar to the oxidative cleavage
of tetraamino-substituted olefins by sulfur to form
thiourea.19,20
Upon addition of a trace amount of water to the NMR
samples, H NMR spectra showed only the N,N-disub-
1
stituted imidazolidinium salt, indicating that the bis-
carbene species react with water. These results are
consistent with the deuterium-labeled experiments.
From the above observations, the pathway of carbene
cleavage shown in Scheme 2 is proposed. The first step
involves a carbene-transfer reaction to form the new
metal carbene complex A.12 By dissociation, the di-
aminocarbene ligand acts as a base which receives a
proton from the solvent to yield the product. It was
demonstrated by theoretical calculations that the simple
diaminocarbenes are strong bases, even stronger than
the imidazolylidene (an aromatic heterocyclic car-
bene).18,6b Thus, when the reaction is carried out in
acetonitrile, the carbene ligand deprotonates the R-pro-
ton of acetonitrile to form the organic salts 14.
Furthermore, the cleavage reaction is accelerated
under acidic conditions. In tetrahydrofuran and 10%
aqueous HBF4, reaction of 1a with Cu(I) is complete
within a few minutes. A catalytic amount of copper ions
(10% mol) can accomplish the same reaction under
acidic conditions. The reaction does not proceed in
aqueous sodium hydroxide solution even with an excess
of metal ion. When the reaction is carried out in air,
the cyclic urea product and imidazolidin-2-ylidinium are
By monitoring the product formation via NMR shifts,
the relative rate of the cleavage of the diaminocarbene
ligand by copper(I) ion was found to decrease in the
order 1a > 4 ∼ 5a > 6a . This may be due to the steric
bulkiness of the phosphine substituent around the
metal, which hinders the access of copper ion to the
carbene ligand. In the carbene-transfer reaction, mono-
denatate phosphine-substituted carbene complexes 5a ,b
undergo a similar reaction, but the phosphine ligand
shifts from tungsten to the new metal center to form
the phosphine-carbene complex (eq 5). Reactions of
5a ,b with (PhCN)2PdCl2 and [(CO)2RhCl]2 gave a mix-
(19) Maas, G.; Singer, B. Chem. Ber. 1983, 116, 3659.
(20) Scho¨nberg, A.; Singer, E.; Stephan, W. Chem. Ber. 1984, 117,
3388.
(18) Dixon, D. A.; Arduengo, A. J ., III. J . Phys. Chem. 1991, 95, 4180.

2150 Organometallics, Vol. 18, No. 11, 1999
Ta ble 4. Cr ysta l Da ta for 5b, 6b, a n d 11c
Ku et al.
5b
6b
11c
formula
Mw
C
39H33N2O4PW
C47H44Cl2N2O3P2Pt
1001.53
C37H37Cl6N2PPt
948.45
808.49
wavelength (Å)
diffractometer
temp (K)
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
0.710 73
SMART CCD
295
monoclinic P21/n
9.7397(1)
19.1681(3)
18.5351(2)
90
95.986(1)
90
3441.48(7)
4
0.710 73
SMART CCD
295
monoclinic P21/n
9.5156(1)
34.0463(1)
14.4135(1)
90
107.855(1)
90
4444.68(6)
4
1.497
2.833
0.710 73
SMART CCD
295
monoclinic Cc
19.0067(3)
12.6343(2)
16.9999(1)
90
101.66
90
3998.07(9)
4
1.576
Z
D
calcd (Mg/m3)
1.560
3.446
abs coeff (mm-1
)
3.979
F(000)
1608
2008
1872
crystal size, mm3
θ range
0.225 × 0.10 × 0.07
1.53-27.5
63 738
7094 (Rint ) 0.1104)
Sadabs
0.40 × 0.40 × 0.20
1.20-27.5
57 034
10207 (Rint ) 0.0529)
Sadabs
0.075 × 0.1 × 0.2
1.95-27.46
12 926
7685 (Rint ) 0.0371)
Semiempirical from π-scan
0.3499-0.2309
no. of reflns collected
no. of ind reflns
abs corr
transmission range
refinement method
goodness of fit on F2
final R indices [I > 2σ(I)]
0.7691-0.5743
0.6195-0.3759
full-matrix least-squares on F2
1.154
1.037
0.798
R1 ) 0.0466
wR2 ) 0.1035
0.000 00(6)
R1 ) 0.0621
wR2 ) 0.0903
0.000 28(9)
R1 ) 0.0318
wR2 ) 0.0573
0.000 03(3)
extinction coeff
largest diff peak and hole
0.957 and 1.235 e Å-3
0.840 and -1712 e Å-3
0.738 and -0.522 e Å-3
ture of products which were not easy to purify. However,
NMR showed the disappearance of the starting carbene
5a ,b, indicating carbene transfer. In the bisphosphine-
substituted carbene complexes 6a ,b, reactions gave the
simple bisphosphine metal complexes 20 accompanied
by formation of imidazolidin-2-ylidinium salt (eq 6).
Ta ble 5. Cr ysta l Da ta for 1c a n d 9c
1c
9c
formula
C
22H18N2O5W
C18H18Cl2N2OPt
monoclinic P21/c
20.498(4)
10.704(3)
8.782(2)
101.60(2)
1887.6(8)
4
space group
a (Å)
monoclinic P21/c
8.396(2)
6.345(3)
41.024(7)
92.51(2)
2183(1)
4
b (Å)
c (Å)
â (deg)
V (Å3)
Z
Dcalcd
1.747
1.916
F(000)
1108
1034
2θ range, deg
scan type
µ, cm-1
16.00-25.90
15.20-30.76
ω
θ/2θ
54.359
78.032
crystal size, mm3
scan width (deg)
transmission range
no. of reflns measd
no. of reflns obsda
no. of unique reflns
computation
no. params
R
0.45 × 0.30 × 0.28
0.50 + 0.35 tan θ
0.126-0.320
3844
2903
3644
NRVSDP-VAX
272
0.027
0.20 × 0.30 × 0.50
0.80 + 0.35 tan θ
0.422-1.000
3332
2349
3332
NRVSDP-VAX
218
0.046
Rw
0.029
0.044
S
1.49
2.03
a I > 2σ(I)
cis and facial in 5b and 6b, respectively. All bond
distances and bond angles lie within the normal range,
except that of W-Ccarbene. WdC bond lengths are in the
range 2.276-2.290 Å and are somewhat longer than
those of Fischer-type carbenes, but are similar to those
of diaminocarbene complexes,21 indicating a resonance
contribution of the amino group to the carbene cen-
ter.5-7,22 This suggests that the diaminocarbene ligand
is a good σ-donor, which shortens the bond distance of
carbonyl ligands trans to the carbene moiety (Table 6).
The platinum is square planar in complexes 9c and
11b (Figures 4 and 5). The bond lengths PtdC, Pt-P,
Cr ysta llogr a p h y. Single crystals suitable for X-ray
analysis of complexes 1c, 5b, 6b‚CH2Cl2, 9c, and 11b‚
2CH2Cl2 are obtained by slow evaporation of dichloro-
methane/hexane solutions. The crystal data are given
in Tables 4 and 5. ORTEP drawings of 1c, 5b, 6b, 9c,
and 11b are depicted in Figures 1-5, respectively, and
selected bond distances and bond angles are sum-
marized in Table 6.
All tungsten complexes are octahedral. The stereo-
chemistry of diaminocarbene and phosphine ligands is
(21) O¨ fele, K.; Herrmann, W. A.; Mihalios, D.; Elison, M.; Herdtweck,
E.; Scherer, W.; Mink, J . J . Organomet. Chem. 1993, 459, 177.

Cleavage of Diaminocarbene Ligands
Organometallics, Vol. 18, No. 11, 1999 2151
F igu r e 1.
F igu r e 3.
F igu r e 2.
and Pt-Cl are typical and are in good agreement with
those in platinum-aminocarbene complexes.23 The metal
to the carbene center distance in 11b [1.970(6) Å] is
slightly longer than that in 21 [1.94 Å, average].
F igu r e 4.
Su m m a r y
Diaminocarbene transfer from a group VI metal
center to another metal (Pd, Pt, Rh, Au) has been shown
to be a viable synthetic approach for the preparation of
metal carbene complexes. Copper and silver carbene
species can be prepared similarly, but subsequently
decompose to yield an iminium salt.
F igu r e 5.
Exp er im en ta l Section
ses were determined with a Perkin-Elmer 240C instrument.
Conductivities were measured in 10-3 M solution on a Suntex
conductivity meter (SG 17A).
Gen er a l In for m a tion . NMR spectra were recorded on
Bruker AC-E 200 or AM-300 spectrometers. Elemental analy-
(22) Arduengo, A. J ., III; Dias, H. V. R.; Dixon, D. A.; Harlow, R.
L.; Klooster, W. T.; Koetzle, T. F. J . Am. Chem. Soc. 1994, 116, 6812.
(23) (a) Bertani, R.; Mozzon, M.; Michelin, R. A.; Benetollo, F.;
Bombieri, G.; Castilho, T. J .; Pombeiro, A. J . L. Inorg. Chim. Acta 1991,
189, 175. (b) Manabe, N.; Yasui, M.; Nishiyama, H.; Shimamoto, S.;
Matsumura, N.; Iwasaki, F. Bull. Chem. Soc. J pn. 1996, 69, 2771.
All reactions, manipulations, and purification steps were
performed under a dry nitrogen atmosphere. Tetrahydrofuran
was distilled under nitrogen from sodium benzophenone ketyl.
Dichloromethane and acetonitrile were dried with CaH2 and
distilled under nitrogen. Other chemicals and solvents were

2152 Organometallics, Vol. 18, No. 11, 1999
Ta ble 6. Selected Bon d Dista n ces (Å) for 1c, 5b, 6b, 9c, a n d 11b
Ku et al.
1c, M ) W
5b, M ) W
6b, M ) W
9c, M ) Pt
11b, M ) Pt
MdC
2.276(5)
2.280(6)
2.551(2)
2.290(5)
2.560(1)
2.512(1)
1.952(6)
1.969(6)
1.968(6)
1.97(1)
1.970(6)
2.242(2)
M-P
M-P1
M-C1
2.010(7)
2.021(7)
1.991(6)
2.034(6)
2.010(7)
1.347(7)
1.334(7)
2.015(8)
2.021(8)
1.980(7)
1.967(7)
1.83(2)
M-C2
M-C3 (trans to carbene)
M-C4
M-C5
C-N1
C-N2
M-C11
M-C12
1.348(8)
1.341(7)
1.347(7)
1.345(7)
1.37(2)
1.33(2)
2.283(3)
2.348(4)
1.338(7)
1.337(9)
2.366(2)
2.364(2)
obtained from commercial sources and used without further
purification. Complexes 1a ,b, 2a ,b, 3a ,b, and 4 were prepared
by a method previously reported.11 (PhCN)2PdCl2 and (PhCN)2-
PtCl2 were prepared as previously described.24
dichloromethane and recrystallized from dichloromethane/
hexane to give the desired products as solids.
cis-Tetr a ca r bon yl(1,3-d ieth ylim id a zolid in -2-ylid en e)-
(tr ip h en ylp h osp h in e)tu n gsten (5a ). A yellow solid (96%):
mp 140-141 °C (dec); IR (CH2Cl2) νCO ) 2002, 1874, 1853 cm-1
;
P en t a ca r b on yl(1,3-d ib en zylim id a zolid in -2-ylid en e)-
tu n gsten (1c). A solution of (CO)5WdC[NHCH2]211 (2.0 g, 5.07
mmol) and sodium hydride (1.24 g, 50.6 mmol) in THF (100
mL) was stirred at room temperature for 24 h. Benzyl chloride
(2.57 g, 20.3 mmol) was added to the reaction mixture, and
the resulting solution was then kept stirring for another 2 h.
Water (2 mL) was slowly added to quench the excess sodium
hydride at an ice-cooled temperature. After evaporation of
solvent, the residue was chromatographed on silica gel (50 g).
Elution with ethyl acetate/hexane (1:4) gave a yellow band,
which afforded 1c as a yellow solid (2.4 g, 83%): mp 147-149
1H NMR (CDCl3) δ 7.45-7.35 (m, 15 H, Ar-H), 3.43-3.21 (m,
8 H, -CH2-), 1.02 (t, J ) 10 Hz, 6 H); 13C NMR δ 214.1 (J P-C
) 8.4 Hz, J W-C ) 93.7 Hz, WdC), 209.1, 208.4, 204.8 (W-
CO), 136.9, 134.1, 130.2, 128.7, 48.1, 47.9, 13.9; 31P NMR δ
25.0 (J P-W ) 229 Hz). Anal. Calcd for C29H29N2O4PW: C, 50.90;
H, 4.27; N, 4.09. Found: C, 50.11; H, 4.17; N, 4.14.
cis-Tetr acar bon yl(1,3-diben zylim idazolidin -2-yliden e)-
(tr ip h en ylp h osp h in e)tu n gsten (5b). A yellow solid (87%):
mp 223-226 °C (dec); IR (CH2Cl2) νCO ) 2004, 1876, 1854 (sh)
1
cm-1; H NMR (acetone-d6) δ 7.52-7.17 (m, 25 H), 4.51 (br,
1
°C (dec); IR(CH2Cl2) νCO )2064, 1922 cm-1; H NMR (CDCl3)
4H), 3.13 (s, 4 H); 13C NMR (acetone-d6) δ 217.6 (J P-C ) 6.9
Hz, WdC), 208.4, 208.1, 204.3, 137.5, 136.9, 134.2, 133.7,
130.4, 129.2, 128.9, 128.8, 128.7, 128.3, 128.1, 57.6, 48.9; 31P
NMR δ 24.3 (J P-W ) 228 Hz). Anal. Calcd for C39H33N2O4PW:
C, 57.94; H, 4.11; N, 3.46. Found: C, 57.58; H, 3.99; N, 3.56.
δ 7.43-7.23 (m, 10 H), 5.02 (s, 4 H, PhCH2-), 3.32 (m, 4 H,
-NCH2-); 13C NMR δ 209.1, 200.8, 197.8, 135.9, 128.8, 128.0,
127.6, 57.1, 48.1. Anal. Calcd for C22H18N2O5W: C, 46.02; H,
3.16; N, 4.88. Found: C, 45.83; H, 2.95; N, 4.89.
P e n t a ca r b on yl[1,3-b is(4-p e n t e n yl)im id a zolid in -2-
ylid en e]tu n gsten (1d ). Preparation of this compound is
similar to the procedure for complex 1c except 4-pentenyl
iodide was used. Complex 1d : yellow viscous liquid (67%); IR
fa c-(1,3-Die t h ylim id a zolid in -2-ylid e n e ){P ,P ′-b is(d i-
p h en ylp h osp h in o)eth a n e}tr ica r bon yltu n gsten (6a ). A
light brown solid (87%): mp 160-163 °C (dec); IR (CH2Cl2)
1
νCO ) 1919, 1820 cm-1; H NMR (CDCl3) δ 7.76-7.27 (m, 20
1
(CH2Cl2) νCO ) 2062, 1919 cm-1; H NMR (CDCl3) δ 5.78 (m,
H), 3.32 (s, 4 H), 3.28 (q, J ) 7.1 Hz, 4 H), 2.52 (m, 2 H), 2.18
2 H, CH2CHdCH2), 5.09-4.95 (m, 4 H, CH2CHdCH2), 3.69
(m, 4 H,-NCH2-CH2-), 3.54 (s, 4 H, -NCH2-), 2.11 (m, 4 H,
-CH2-CHdCH2), 1.70 (m, 4 H, -NCH2CH2CH2-); 13C NMR δ
207.2, 201.1, 198.0, 137.2, 115.4, 52.7, 48.0, 30.7, 27.3. Anal.
Calcd for C18H22N2O5W: C, 40.77; H, 4.18; N, 5.28. Found: C,
40.47; H, 4.09; N, 5.11.
(m, 2 H), 0.86 (t, J ) 7.1 Hz, 6 H); 13C NMR δ 217.8 (J P-C
)
8 Hz), 216.1 (J
) 35, 10 Hz), 210.8 (J P-C ) 6 Hz, WdC),
P-C
137.8-128. 4 (aromatic-C), 48.3, 48.2, 31.2 (J P-C ) 23 Hz),
13.8; 31P NMR δ 36.9 (J P-W ) 213 Hz). Anal. Calcd for
C
36H38N2O3P2W: C, 54.56; H, 4.83; N, 3.53. Found: C, 54.19;
H, 4.72; N, 3.27.
P en t a ca r b on yl[1,3-d ib en zylim id a zolid in -2-ylid en e]-
10
fa c-(1,3-Dib en zylim id a zolid in -2-ylid en e){P ,P ′-b is(d i-
p h en ylp h osp h in o)eth a n e)tr ica r bon yltu n gsten (6b). A
light brown solid (96%): mp 180-183 °C (dec); IR (CH2Cl2)
νCO ) 1921, 1824 cm-1; 1H NMR (CD3COCD3) δ 7.84-7.10 (m,
30 H), 4.34 (s, 4 H), 3.15 (s, 4 H), 2.63 (m, 2 H), 2.37 (m, 2 H);
13C NMR δ 220.8 (J P-C ) 7.6 Hz), 215.6 (J P-C ) 34, 10 Hz),
210.2 (J P-C ) 6 Hz), 137.1-127.7 (aromatic-C), 52.7, 48.4, 30.4
(J P-C ) 18 Hz); 31P NMR δ 36.1 (J P-W ) 213 Hz). Anal. Calcd
for C46H42N2O3P2W: C, 60.27; H, 4.62; N, 3.06. Found: C, 60.98;
H, 4.61; N, 3.03.
ch r om iu m (3c). A mixture of (CO)5CrdC[NHCH2]2 (3.0 g,
11.5 mmol) and sodium hydride (1.66 g, 69.2 mmol) in THF
was stirred at room temperature overnight. Benzyl chloride
(3.53 g, 27.6 mmol) was added to the reaction mixture, and
the resulting solution was kept stirring for another 12 h. Water
(2 mL) was added slowly to quench the excess sodium hydride
at an ice-cooled temperature. The organic layer was separated,
and the water layer was washed with dichloromethane (20 mL
× 2). The combined organic extracts were dried and concen-
trated. The residue was chromatographed on silica gel (100 g)
with hexane/ethyl acetate (5:1) as the eluent. A light yellow
band was collected and concentrated to give the desired
product 3c as a yellow solid (4.56 g, 89%): mp 172-173 °C
Gen er a l P r oced u r e for Ca r ben e Tr a n sfer . Diaminocar-
bene group VI complexes (1-3) and a 0.5 equimolar amount
of (PhCN)2PdCl2, (PhCN)2PtCl2, [(CO)2RhCl]2, or (Me2S)AuCl
were combined in dichloromethane at room temperature for
0.5 h. During the reaction, carbon monoxide gas was released
and a dark material precipitated. After filtration, ether was
added to precipitate the desired carbene complex from the
solution. Recrystallization of the product from dichloromethane/
hexane or chromatography on silica gel with hexane/ethyl
acetate as the eluent yielded the pure product. Reactions of
1a with (PhCN)2PdCl2 and 1b with (PhCN)2PtCl2 in equal
molar ratio were carried out in refluxing chloroform. Spectral
data of 7a ,b, 9a , 10a ,b, 12a , and 13a as well as crystal data
of 7a and 9a were reported previously.12
1
(dec); IR(CH2Cl2) νCO ) 2056, 1924 cm-1; H NMR (CDCl3) δ
7.46-7.30 (m, 10 H), 5.08 (s, 4 H, PhCH2-), 3.29 (m, 4 H,
-NCH2-); 13C NMR δ 221.6, 221.5, 217.5, 136.0, 128.8, 127.9,
127.5, 55.8, 48.5. Anal. Calcd for C22H18N2O5Cr: C, 59.73; H,
4.10; N, 6.33. Found: C, 59.34; H, 3.87; N, 6.35.
Gen er a l P r oced u r e for P h osp h in e-Su bstitu ted Ca r -
ben e Com p lexes. A mixture of diaminocarbene complex and
an equimolar amount of phosphine was heated at 120 °C for
1 h under nitrogen. The reaction mixture was dissolved in
(24) Anderson, G. K.; Lin, M. Inorg. Synth. 1990, 28, 61.

Cleavage of Diaminocarbene Ligands
Organometallics, Vol. 18, No. 11, 1999 2153
Bis(1,3-d iben zylim id a zolid in -2-ylid en e)d ich lor op a lla -
d iu m (II) (7c). A light gray solid (83%): mp 234-238 °C (dec);
1H NMR (CDCl3) δ 7.43 (m, 12 H), 7.25 (m, 8 H), 5.23 (s, 8 H),
3.30 (s, 8H); 13C NMR δ 199.1, 136.8, 129.3, 129.2, 128.5, 53.9,
48.5. Anal. Calcd for C33H34N4Cl2Pd: C, 59.70; H, 5.16; N, 8.44.
Found: C, 59.33; H, 4.89; N, 8.11.
filtered through Celite, and the filtrate was concentrated. The
residue was dissolved in dichloromethane, and ether was
added to precipitate the desired complex as a yellow solid
(74%): mp 136-138 °C (dec); 1H NMR (CDCl3) δ 5.69-5.61
(m, 2 H), 5.28-5.10 (m, 4 H), 4.55-4.35 (m, 2 H), 3.94 (m, 4
H), 3.67-3.41 (m, 12 H), 3.12 (d, J ) 11.8 Hz, 2 H), 2.85 (d, J
) 8 Hz, 2 H); 13C NMR δ 202.8 (J Rh-C ) 30.3 Hz), 131.8, 119.1,
67.3 (J Rh-C ) 7.8 Hz), 52.9, 50.8, 50.6 (J Rh-C ) 7.7 Hz), 49.2,
47.7; conductivity 62 Ω-1 cm2 mol-1 (1 × 10-3 M in CH3OH).
Anal. Calcd for C18H28ClN4Rh: C, 49.27; H, 6.43; N, 12.77.
Found: C, 49.01; H, 6.02; N, 12.43.
Bis{1,3-di(4-pen ten yl)im id a zolid in -2-ylid en e}d ich lor o-
p a lla d iu m (II) (7d ). A light yellow viscous liquid (96%) after
chromatography on silica gel: 1H NMR (CDCl3) δ 5.82 (m, 4
H), 4.94 (m, 8 H), 3.98 (m, 8 H), 3.52 (s, 8 H), 2.15 (m, 8 H),
1.85 (m, 8 H); 13C NMR 198.6 (PddC), 137.6, 114.9, 49.3, 48.4,
31.0, 27.3; FABMS m/z ) 553.0 (M - 35Cl). Anal. Calcd for
B is (1,3-d ib e n zy lim id a zo lid in -2-y lid e n e )c a r b o n y l-
ch lor or h od iu m (I) (12c). Preparation of 12c follows the same
procedure for 12b. A yellow solid (66%): mp 142-145 °C (dec);
C
26H44N4PdCl2: C, 52.93; H, 7.52; N, 9.50. Found: C, 52.77;
H, 7.50; N, 9.14.
IR (CHCl3) νCO ) 1947 cm-1
;
1H NMR (CDCl3) δ 7.43-7.19
(1,3-Dib en zylim id a zolid in -2-ylid en e)ca r b on yld ich lo-
r op la tin u m (II) (9c). A yellow solid (78%): mp 131-133 °C
(dec); IR (CH2Cl2) νCO ) 2106 cm-1; 1H NMR (CDCl3) δ 7.35-
7.21 (m, 10 H, Ar-H), 5.03 (m, 4 H, -CH2Ph), 3.63 (s, 4 H);
13C NMR δ 168.2 (J Pt-C ) 1134 Hz), 154.0 (J Pt-C ) 1735 Hz),
133.7, 129.2, 128.7, 128.2, 54.1 (J Pt-C ) 54.0 Hz), 48.5 (J Pt-C
) 48.7). Anal. Calcd for C18H18Cl2N2OPt: C, 39.72; H, 3.33;
N, 5.15. Found: C, 39.31; H, 3.12; N, 5.25.
{1,3-Di(4-p en t en yl)im id a zolid in -2-ylid en e }ca r b on yl-
d ich lor op la tin u m (II) (9d ). A yellow solid (79%): mp 145-
147 °C (dec); IR (CH2Cl2) νCO ) 2105 cm-1; 1H NMR (CDCl3) δ
5.79 (m, 2 H), 5.04 (m, 4 H), 3.87-3.63 (m, 8 H), 2.10 (m, 4
H), 1.80 (m, 4 H); 13C NMR δ 167.4 (PtdC), 154.4, 136.7, 115.8,
49.6, 48.6, 30.5, 26.6. Anal. Calcd for C14H22Cl2N2OPt: C,
33.61; H, 4.43; N, 5.60. Found: C, 34.11; H, 4.27; N, 5.80.
{1,3-Di(4-p en t en yl)im id a zolid in -2-ylid en e}d ich lor o-
p la tin u m (II) (10d ). A solution of 9d (0.1 g, 0.2 mmol) in
chloroform (5 mL) was heated to reflux for 2 h. After concen-
tration of the reaction mixture volume to 1 mL, ether (20 mL)
was added to precipitate the desired complex. Upon filtration,
9d was obtained as a viscous yellow liquid (82 mg, 87%):1H
NMR (CDCl3): δ 5.86-5.73 (m, 1 H), 5.04 (m, 2 H), 4.50 (m, 1
H), 3.72-3.57 (m, 7 H), 3.23-3.17 (m, 1 H), 2.30 (m, 2 H), 2.08
(m, 4 H), 1.65 (m, 2), 1.40-1.19 (2 H); 13C NMR δ 169.7(PtdC),
136.9, 115.6, 88.4, 69.0, 49.4, 48.7, 45.4, 31.1, 30.6, 26.7, 21.1.
Anal. Calcd for C13H22N2Cl2Pt: C, 33.06; H, 4.69; N, 5.93.
Found: C, 33.31; H, 4.87; N, 5.81.
2
(m, 20 H, Ar-H), 5.60 (d, J H-H ) 14.8 Hz, 4 H, N-CHH-
2
Ph), 4.95 (d, J H-H ) 14.8 Hz, 4 H, N-CHH-Ph), 3.99 (m, 8
H, N-CH2-); 13C NMR δ 212.4 (d, J Rh-C ) 37.7 Hz, RhdC),
187.4 (d, J Rh-C ) 83.6), 136.8, 128.5, 128.3, 127.4, 54.6, 48.0.
Anal. Calcd for C35H36ClN4ORh: C, 63.02; H, 5.44; N, 8.40.
Found: C, 62.98; H, 5.15; N, 8.22.
Bis{1,3-d i(4-p e n t e n yl)im id a zolid in -2-ylid e n e}}ca r -
bon ylch lor or h od iu m (I) (12d ). Preparation of 12c follows
the same procedure for 12b. A yellow liquid (68%): IR (CHCl3)
νCO ) 1942 cm-1; 1H NMR (CDCl3) δ 5.82 (m, 4 H, CH2dCH),
4.98 (m, 8 H, CH2dC), 4.28 (m, 4 H, N-CHH-), 3.70 (m, 4 H,
N-CHH-), 3.56 (m, 8 H, N-CH2CH2-), 2.11 (m, 8 H, d
CHCH2-), 1.76 (m, 8 H, NCH2CH2-); 13C NMR 212.5 (d, J Rh-C
) 36.4 Hz, RhdC), 187.3 (d, J Rh-C ) 83.0 Hz, Rh-CO), 138.0,
114.5, 50.0, 48.4, 31.1, 27.3; FABMS m/z [C27H44N4O35Cl103
-
Rh] ) 578, 550 [M+ - CO]. Anal. Calcd for C27H44ClN4ORh:
C, 56.01; H, 7.66; N, 9.68. Found: C, 56.24; H, 7.43; N, 9.33.
Bis(1,3-d ia llylim id a zolid in -2-ylid en e)gold (I) Ch lor id e
(13b). A mixture of 1b (47.4 mg, 0.1 mmol) and (Me2S)AuCl
(14.7 mg, 0.05 mmol) in dichloromethane (10 mL) was stirred
at room temperature for 2 h. The reaction mixture was filtered
through a short column of silica gel (3 g) and washed with
ethyl acetate (20 mL). The filtrate was concentrated to give
13b as a yellow liquid (37.1 mg, 70%). 1H NMR (CDCl3) δ 5.79
(m, 4 H), 5.22 (m, 8 H, dCH2), 4.15 (m, 8 H, -CH2CHd), 3.70
(s, 8 H, -CH2N-); 13C NMR δ 205.1 (AudC), 132.1, 119.1, 52.6,
49.1; FABMS m/z for [C18H28N4197Au]+ ) 497.1; conductivity
62 Ω-1 cm2 mol-1 (1 × 10-3 M in MeOH). Anal. Calcd for
C18H28N4ClAu: C, 40.57; H, 5.30; N, 10.51. Found: C, 40.13;
H, 5.56; N, 10.22.
cis-(1,3-Dieth ylim id a zolid in -2-ylid en e)(tr ip h en ylp h os-
p h in e)d ich lor op la tin u m (II) (11a ). A chloroform solution of
9a (120 mg, 0.28 mmol) and triphenylphosphine (75 mg, 0.28
mmol) was stirred for 5 min. The reaction mixture was
concentrated and the residue was recrystallized from dichloro-
methane/hexane to yield 11a as a white solid (168 mg, 92%):
Bis(1,3-d iben zylim id a zolid in -2-ylid en e)gold (I) Ch lo-
r id e (13c). The procedure is similar to that for 13b. A yellow
liquid (56%): 1H NMR (CDCl3) δ 7.24 (m 20 H), 4.73 (s, 8 H),
3.60 (s, 8 H); 13C NMR δ 204.4 (AudC), 134.8, 129.0, 128.4,
127.6, 54.2, 49.1; FABMS m/z for [C34H36N4197Au] ) 697.1;
conductivity 59 Ω-1 cm2 mol-1 (1 × 10-3 M in MeOH). Anal.
Calcd for C33H34N4ClAu: C, 55.12; H, 4.77; N, 7.79. Found: C,
55.35; H, 4.66; N, 7.30.
B i s {1,3-d i (4-p e n t e n y l)i m i d a z o li d i n -2-y li d e n e }}-
gold (I) Ch lor id e (13d ). The procedure is similar to that for
13b. A yellow liquid (77%): 1H NMR (CDCl3) δ 5.75 (m, 4 H),
5.05 (m, 8 H), 3.69 (s, 8 H), 3.56 (t, J ) 7.1 Hz, 8 H), 2.08 (m,
8 H), 1.66 (m, 8 H); 13C NMR δ 204.2 (AudC), 136.9, 115.7,
49.6, 48.8, 30.5, 27.2; FABMS m/z for [C26H44N4197Au]+ ) 609.2.
Conductivity: 58 Ω-1 cm2 mol-1 (1 × 10-3 M in MeOH). Anal.
Calcd for C26H44N4ClAu: C, 48.41; H, 6.87; N, 8.69. Found: C,
48.02; H, 6.55; N, 8.44.
1,3-Diet h ylim id a zolid in -2-ylid in iu m Tet r a flu or ob o-
r a te (14a ). A mixture of 1a (300 mg, 0.67 mmol) and Cu(CH3-
CN)BF4 (210 mg, 0.67 mmol) in chloroform was heated to
reflux for 4 h. After concentration of the reaction mixture, the
residue was chromatographed on alumina (10 g) and eluted
with dichloromethane/ethyl acetate. The desired product 14a
was obtained as a yellow liquid (121 mg, 85%): 1H NMR
(CDCl3) δ 8.15 (s, 1 H, -NCHN-), 3.94 (s, 4 H), 3.55 (q, J )
7.2 Hz, 4 H), 1.31 (t, J ) 7.2 Hz, 6 H); 13C NMR δ 156.3, 48.1,
1
mp 125-128 °C (dec); H NMR (CDCl3): δ 7.72-7.33 (m, 15
H), 4.18 (dq, J ) 7.2, 2.4 Hz, 2 H), 3.37 (m, 2 H), 3.04 (dq, J
) 7.2, 2.4 Hz, 2 H), 2.76 (m, 2 H), 1.04 (t, J ) 7.2 Hz, 6 H); 13
C
NMR δ 176.7 (J P-C ) 6 Hz), 134.3 (d, J P-C ) 10.6 Hz), 131.1,
128.2, 128.0, 46.7, 44.7, 12.4; 31P NMR δ 9.1 (J Pt-P ) 3970 Hz).
Anal. Calcd for C25H29Cl2N2PPt: C, 45.88; H, 4.47; N, 4.28.
Found: C, 45.88; H, 4.29; N, 3.95.
cis-(1,3-Diben zylim idazolidin -2-yliden e)(tr iph en ylph os-
p h in e)d ich lor op la tin u m (II) (11b). A solution of 9c (272 mg,
0.5 mmol) and triphenylphosphine (131 mg, 0.5 mmol) in
chloroform was stirred for 5 min. The reaction mixture was
concentrated, and the residue was recrystallized from dichloro-
methane/hexane to yield 11b as needlelike crystals (380 mg,
97%): mp 136-139 °C (dec); 1H NMR (CDCl3) δ 7.74-7.21 (m,
25 H), 5.64 (d, J ) 14.1, 2 H), 3.95 (d, J ) 14.1, 2 H), 3.03 (m,
2 H), 2.66 (m, 2 H); 13C NMR (125 MHz) δ 178.1 (J P-C ) 6.3
Hz), 134.5 (J P-C ) 10 Hz), 134.4, 131.2, 129.9, 129.4, 129.0,
128.5, 128.2, 54.8, 47.1; 31P NMR δ 9.69 (J Pt-P ) 3928 Hz).
Anal. Calcd for C35H33Cl2N2PPt: C, 53.99; H, 4.27; N, 3.60.
Found: C, 53.97; H, 4.16; N, 3.08.
Bis(1,3-d ia llylim id a zolid in -2-ylid en e)r h od iu m (I) Ch lo-
r id e (12b). A mixture of 1b (94.8 mg, 0.2 mmol) and
[(CO)2RhCl]2 (19.5 mg, 0.05 mmol) in dichloromethane (20 mL)
was stirred at room temperature for 48 h. The solution was

2154 Organometallics, Vol. 18, No. 11, 1999
Ku et al.
43.4, 12.8; 19F NMR δ -153.7 (10BF4), -153.8 (11BF4). Anal.
Calcd for C7H15BN2F4: C, 39.29; H, 7.06; N, 13.09. Found: C,
38.89; H, 6.88; N, 12.77.
1,3-Dia llylim id a zolid in -2-ylid in iu m Tetr a flu or obor a te
(14b). This compound was obtained similarly as the procedure
described for 14a . A light yellow liquid (84%): 1H NMR (CDCl3)
δ 8.04 (s, 1 H), 5.80 (m, 2 H), 5.30 (m, 4 H), 4.04 (d, J ) 6.4
Hz), 3.88 (s, 4 H); 13C NMR δ 157.3, 129.8, 121.9, 50.7, 48.1;
19F NMR δ -153.0 (10BF4), -153.1(11BF4). HRFABMS Calcd
for [C9H15N2]+ m/z ) 151.1235. Found: 151.1223.
1,3-Diben zylim id a zolid in -2-ylid in iu m tetr a flu or obo-
r a te (14c). This compound was obtained similarly as the
procedure described for 14a . A light liquid (83%); the spectral
data are similar to the trifluoromethylsulonate salt reported
by Maas and Singer:16 1H NMR (CDCl3) δ 8.49 (s, 1 H), 7.30-
7.16 (m, 10 H), 4.68 (s, 4 H), 3.75 (s, 4 H); 13C NMR δ 157.1,
132.3, 129.0, 128.7, 128.6, 51.9, 47.5; 19F NMR δ -152.0
(10BF4), -152.1(11BF4). HRFABMS Calcd for [C17H19N2]+ m/z
) 251.1548. Found: 251.1539.
Rea ction of Cop p er Ca r ben e Com p lexes w ith O2. A
solution of copper carbene 16a -c in dichloromethane was
exposed to dry air with stirring for several hours. After
concentration, the residue was chromatographed on silica gel
with dichloromethane as eluent. The fraction containing cyclic
urea was collected and concentrated to give the desired product
as a light-yellow liquid. Spectral data of the cyclic urea are
essentially identical to those reported in the literature: 1,3-
diethylimidazolidine-2-one (17a ),25 1,3-diallylimidazolidine-2-
one (17b),26 and 1,3-dibenzylimidazolidine-2-one (17c).25
1,3-Dieth ylim id a zolid in e-2-th ion e (19a ). Complex 6a
(100 mg, 0.12 mmol) was treated with sulfur S8 (10 mg) in
dichloromethane. After stirring for 2 h, the reaction mixture
was concentrated and the residue was chromatographed on
silica gel (20 g) with elution by dichloromethane/ethyl acetate.
The fraction containing compound 19a was collected and
concentrated to give 19a as a white solid (15 mg, 79%): mp
61-62 °C (lit.27 62-63 °C); 1H NMR (CDCl3)28 δ 3.65 (q, J ) 7
Hz, 3.53 (s, 4 H), 1.15 (t, J ) 7 Hz, 6 H); 13C NMR δ 181.8,
45.3, 42.2, 12.0.
Bis(1,3-eth ylim id a zolid in -2-ylid en e)cop p er (I) Tetr a -
flu or obor a te (15a ). A solution of complex 1a (500 mg, 1.11
mmol) and [Cu(CH3CN)4]BF4 (175 mg, 0.56 mmol) in CH2Cl2
(10 mL) was stirred at room temperature for 1 h. The reaction
mixture was concentrated to the volume of 1 mL, and ether
(30 mL) was added to cause the precipitation of white solid.
After washing with ether (10 mL × 2), the white solid was
collected and dried under vacuum (115 mg, 51%). This solid
is extremely sensitive to moisture and slowly decomposes: mp
1,3-Diben zylim id a zolid in e-2-th ion e (19b). The proce-
dure is similar to that for 19a . A white solid (80%): mp 85-
1
86 °C (lit.19 87 °C); H NMR (CDCl3) δ 7.33-7.24 (m, 10 H),
4.88 (s, 4 H), 3.37 (s, 4 H); 13C NMR 183.1, 136.5, 128.2, 127.7,
51.8, 45.3.
Rea ction of Bisp h osp h in e-Su bstitu ted Ca r ben e Com -
p lexes w ith (P h CN)2P d Cl2 a n d (P h CN)2P tCl2. A solution
of 6a or 6b and a 0.5 equimolar amount of (PhCN)2MCl (M )
Pd, Pt) in dichloromethane was heated to reflux for 2 h. During
the reaction period, carbon monoxide gas was released and a
dark material precipitated. Excess NaBF4 was added, and then
the solution was filtered through silica gel (10 g) and washed
with ethyl acetate. The filtrate was concentrated and dissolved
in CDCl3 for 1H and 31P NMR studies. In each case, NMR
spectra show the formation of (dppe)MCl2 and the iminium
salt 14. Chemical shifts of (dppe)PdCl2 (20a )29 and (dppe)PtCl2
(20b)30 are essentially identical to those reported in the
literature.
Cr ysta llogr a p h y. Crystals of 1c, 5b, 6b, 9c, and 11b were
obtained by recrystallization from dichloromethane/hexane.
Cell parameters of 1c and 9c were determined on a CAD-4
diffractometer at room temperature and by a least-squares
treatment, whereas 5b, 6b, and 11b were measured by a
Siemens SMART CCD instrument and refined by full-matrix
least-squares on F2. The crystal data are listed in Tables 4
and 5 and selected bond distances are collected in Table 6.
Other crystallographic data are supplied as Supporting Infor-
mation.
1
49-51 °C (sealed, dec); H NMR (CDCl3) δ 3.61 (s, 8 H), 3.51
(q, J ) 7.6 Hz, 8 H), 1.20 (t, J ) 7.6 Hz, 12 H); 13C NMR δ
197.0 (CudC), 48.6, 45.7, 14.4; 19F NMR δ -154.4 (br).
HRFABMS Calcd for [C14H28N4Cu]+ m/z ) 315.1612. Found:
315.1601.
Bis(1,3-a llylim id a zolid in -2-ylid en e)cop p er (I) Tetr a -
flu or obor a te (15b). This complex was prepared according to
the procedure described for 15a . A white solid (58%): mp 29-
32 °C; 1H NMR (CDCl3) δ 5.76 (m, 4 H), 5.17 (m, 8 H), 3.95 (d,
J ) 5 Hz, 8 H), 3.56 (s, 8 H); 13C NMR δ 198.6 (CudC), 131.4,
117.7, 52.4, 48.6; 19F NMR δ -154.0 (br). FABMS Calcd for
[C18H28N4Cu]+ m/z ) 363.1612. Found: 363.1601.
Bis(1,3-b en zylim id a zolid in -2-ylid en e)cop p er (I) Tet -
r a flu or obor a te (15c). This complex was prepared according
to the procedure described for 15a . A white solid (69%): mp
81-82.5 °C (dec); 1H NMR (CDCl3) δ 7.40-7.28 (m, 20 H), 4.58
(s, 8 H), 3.59 (s, 8 H); 13C NMR δ 197.8 (CudC), 135.2, 129.2,
128.4, 128.2, 54.6, 47.7; 19F NMR δ -154.5 (br). HRFABMS
Calcd for [C34H36N4Cu]+ m/z ) 563.2238. Found: 563.2225.
Sp ectr oscop ic Stu d y of Silver Ca r ben e Com p lexes. A
mixture of chromium carbene complex 3a ,c and an equimolar
amount of AgPF6 was placed in a dried NMR tube in a drybox.
Purified CDCl3 (0.5 mL) was added, and the sample was
checked by NMR and HRFABMS.
Ack n ow led gm en t. Financial support for this work
from the National Science Council (NSC88-2113-M002-
32), Taiwan, ROC, is acknowledged.
Bis(1,3-et h ylim id a zolid in -2-ylid en e)silver (I) H exflu -
or op h osp h a te (16a ): 1H NMR (CDCl3) δ 3.67 (s, 8 H), 3.52
(q, J ) 7.1 Hz, 8 H), 1.23 (t, J ) 7.1 Hz, 12 H); 13C NMR δ
202.5 (AgdC, J 107Ag-C ) 168 Hz, J 109Ag-C ) 192 Hz), 48.4, 45.9,
14.4; 19F NMR δ -74.4 (d, J P-F ) 713.9 Hz). HRFABMS Calcd
for C14H28N4107Ag m/z ) 359.1365. Found: 359.1348.
Bis(1,3-a llylim id a zolid in -2-ylid en e)silver (I) H exflu -
or op h osp h a te (16b): 1H NMR (CDCl3) δ 5.86-5.77 (m, 4 H),
5.27-5.21 (m, 8 H), 4.05 (d, J ) 5 Hz, 8 H), 3.65 (s, 8 H); 13C
NMR δ 204.2 (AgdC, J 107Ag-C ) 169 Hz, J 109Ag-C ) 194 Hz),
132.6, 118.9, 52.1, 49.3; 19F NMR δ -73.9 (d, J P-F ) 711.4 Hz).
HRFABMS Calcd for C18H28N4107Ag m/z ) 407.1365. Found:
407.1344.
Su p p or tin g In for m a tion Ava ila ble: A complete descrip-
tion of the X-ray crystallographic structure determination of
1c, 5b, 6b, 9c, and 11b including tables of crystal data, atomic
coordinates, isotropic and anisotropic thermal parameters, and
1
bond distances and angles and H NMR spectra of 15a -c and
16a -c. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM981023D
(25) Bates, H. A.; Condulis, N.; Stein, N. L. J . Org. Chem. 1986, 51,
2228.
(26) Moreau, B.; Lavielle, S.; Marquet, A. Tetrahedron Lett. 1977,
2591.
(27) Denk, M. K.; Thadani, A.; Hatano, K.; Lough, A. J . Angew.
Chem., Int. Ed. Engl. 1997, 36, 2607.
(28) Li, C.-d.; Mella, S. L.; Sartorelli, A. C. J . Med. Chem. 1981, 24,
1089.
Bis(1,3-ben zylim id a zolid in -2-ylid en e)silver (I) Hexflu -
or op h osp h a te (16c): 1H NMR (CDCl3) δ 7.31-7.18 (m, 20
H), 4.55 (s, 8 H), 3.54 (s, 8 H); 13C NMR δ 203.9 (AgdC, J 107Ag-C
) 170 Hz, J 109Ag-C ) 196 Hz), 135.3, 129.0, 128.2, 127.6, 54.8;
19F NMR δ -73.5 (d, J P-F ) 713.3 Hz). HRFABMS Calcd for
(29) Oliver, D. L.; Anderson, G. K. Polyhedron 1992, 11, 2415.
(30) McCrindle, R.; McAlees, A. J . Organometallics 1993, 12, 2445.
C
34H36N4107Ag m/z ) 607.1991. Found: 607.1987.